The current use of the lifetime and Doppler broadening techniques in defect identification is demonstrated with two studies, the first being the identification of carbon vacancy in n-6H SiC through lifetime spectroscopy, and the second the production of de-hydrogenated voids in alpha -Si:H through light soaking. Some less conventional ideas are presented for more specific defect identification, namely (i) the amalgamation of lifetime and Doppler techniques with conventional deep level transient spectroscopy in what may be called "positron-deep level transient spectroscopy", and (ii) the extraction of more spatial information on vacancy defects by means of what may be called "Fourier transform Doppler broadening of annihilation radiation spectroscopy".